Waste Management System

ABSTRACT

A system and method of integrated waste management having a source of a combustible waste material, a separator for separating the combustible waste material from a recyclable material, an airless drier for drying the combustible waste material to generate a pyrolysis feedstock, and a pyrolyser for pyrolysing the pyrolysis feedstock to form char and pyrogas. The system and method for power generation may also use an oxidiser for the high-temperature oxidation of syngas generated from the pyrolysis feedstock to generate heat for power production.

The present invention relates to a waste management system and to apower generation system including the waste management system. The wastemanagement system of the present invention generally relates to wastematerials which include combustible matter.

The clean, effective and environmentally-friendly disposal of domesticand industrial waste materials, including combustible waste materials,provides on-going challenges for industry, national governments andlocal authorities.

Waste disposal methods such as burying waste in landfills at municipaltips have many drawbacks. These include the need for large tracts ofland which may otherwise be better utilised, the prospect of wind-blownlitter, the attraction to rats and other vermin which may provide ahealth risk to the community, unpleasant odours and the generation ofgreenhouse gases such as methane which may result from thebiodegradation of waste.

Other disposal methods include incineration which involves thecombustion of the waste material. Although often convenient for thedisposal of hazardous materials, incineration is an unpopular method ofwaste disposal where there is the prospect of toxic gases and otherpollution being released into the atmosphere. Traditional incineratorsare also known to have large carbon footprints and high profiles.

As an alternative to the waste disposal methods outlined above, the useof combustible waste materials as fuels for generating energy is known.In a world of diminishing fossil fuel reserves, the uncertainty ofregular supplies of gas and oil often due to geopolitical factors, andthe environmental risks posed by nuclear energy, generating energy fromwaste materials is considered an attractive field of endeavour. This isbecause it addresses both the problems of waste management and theprovision of alternative fuel sources. However, many of the knownmethods are resource, cost and energy inefficient. Accordingly,alternative means of waste management and the conversion of wastematerials into sources of energy have been sought which are resource,cost and energy efficient. The present invention aims to achieve some ofthese means.

According to the present invention there is provided an integrated wastemanagement system, comprising:

a source of a combustible waste material;

a separator for separating the combustible waste material from arecyclable material;

an airless drier for drying the combustible waste material to generate apyrolysis feedstock; and

a pyrolyser for pyrolysing the pyrolysis feedstock to form char andpyrogas.

Further according to the invention, there is provided an integratedmethod of waste management comprising:

(a) providing a source of a combustible waste material;

(b) optionally separating the combustible waste material from arecyclable material present in the source;

(c) drying the combustible waste material in an airless drier togenerate a dried pyrolysis feedstock; and

(d) pyrolysing the dried pyrolysis feedstock to form char and pyrogas.

The integrated system and method of waste management of the presentinvention provide a cost and energy efficient means of processingindustrial and domestic waste materials, whereby combustible materialssuitable for downstream conversion into energy are obtained and wastematerials not considered suitable for energy conversion, but which arerecyclable, can be separated and processed separately in a recyclingplant. Accordingly, minimal compromise of eco-friendly recycling effortscan be achieved with the present invention thus contributing to theoverall ecological benefits of waste material processing.

Pyrolytic processes are generally more efficient the lower the moisturecontent of the material being pyrolysed. In the present invention, theuse of an airless drier provides significant overall energy savings interms of running the system, as approximately 30% less energy isrequired to operate an airless drier per unit weight of material beingdried compared to a conventional air drier. Furthermore, reduced wastematerial drying times typically of 40 to 50 minutes less are requiredwith the airless drier compared with other forms of drying, therebyadding to the overall efficiency of the system in terms of processingtimes.

Further according to the invention, there is provided a power generationsystem comprising the waste management system according to the inventionand further comprising an oxidiser for the high-temperature oxidation ofsyngas and pyrogas generated from the pyrolysis feedstock to generateheat for power production.

Even further according to the invention, there is provided a method ofpower generation according to the invention comprising the integratedmethod of waste management according to the invention, and preferablyfurther comprising the steps of:

(d) gasifying the char to generate syngas; and

(e) oxidising the syngas and/or pyrogas at high-temperature in anoxidiser to generate heat for power generation.

By having an integrated power generation system comprising an integratedwaste management system according to the invention, all of the stepsfrom the deposit at a waste processing plant of a source of acombustible waste material through to power generation (eg, electricalpower generation from a conventional steam turbine unit) can be carriedout at one site. This provides significant cost and resource savingsbecause it reduces transportation costs (eg, between a waste separationplant, a waste drying plant and pyrolysis, gasification andoxidation/power generation plants) and it also enables improved overallenergy efficiency through the provision of heat energy feedback loopsbetween the various components of the systems.

Furthermore, combustion processes known in the art for power generationgenerally undergo pyrolysis, gasification and oxidation of syngas (orother combustion gases) as a single step process. In contrast, thesystem and method of power generation according to the present inventionis adapted to separate the pyrolysis of a dried waste material pyrolysisfeedstock, the gasification of the pyrolysis products and oxidation ofthe combustible gases from the gasification step. This allows a highdegree of control over each step than in a single step process such asthat which takes place in a conventional mass burn incinerator used forpower generation.

Furthermore, in the present invention, preferably all of the combustiblewaste material is heated in the pyrolyser or gasifier to a uniformtemperature (typically 250 to 600° C.) not exceeding 900° C. Inconventional incineration on a hearth, there are often hot spots andcold spots resulting in some combustible waste material not being heatedsufficiently and remaining unburnt in the resulting ash residue.Conversely, some of the combustible waste material may be overheated andmay release toxic gaseous combustion by-products. In contrast, in thepresent invention it can be ensured that substantially all of thecombustible waste material is thermally decomposed in the pyrolyser orgasifier. Also, that essentially none of the combustible waste materialis overheated so that gaseous and/or volatile toxic pollutants are keptto a minimum.

Additionally, in accordance with the invention, combustion (oxidation)in the oxidiser is with a medium calorific value gas (ie, syngas and/orpyrogas) in a highly controlled oxidising environment with uniformoxidation temperatures. In this manner, hot spots and cold spots areagain kept to a minimum or eliminated compared to the combustion zone ina conventional mass burn incinerator thereby resulting in substantiallycomplete combustion of the gases with lower concentrations of carbonmonoxide and volatile organic compounds in the exhaust gases emanatingfrom the oxidiser. Furthermore, a uniform oxidation temperature resultsin the generation of lower levels of temperature-generated nitrogenoxides (thermal NO_(x)), while the pyrolysis and gasification processesdue to their reducing nature subdue the generation of fuel-generatednitrogen oxides (fuel NO_(x)). Accordingly, the nitrogen oxide levels inthe exhaust gases of the oxidiser used in the present invention aretypically lower than that of a conventional mass burn incinerator.

Preferably, the separator used in accordance with the inventioncomprises one or more of a trommel, a magnetic separator, a ballisticseparator, an eddy current separator, optical separation means and ashredder. This enables the adaptability of the invention to separatingdifferent types of waste dependent upon the waste composition. Forexample, waste from a source containing only household biowaste andpaper-based waste may typically only require a separator comprising atrommel and a shredder. On the other hand, the same household biowastewhich also contained recyclable plastics materials (eg, bottles, foodwrappers, etc) may also include an automated optical separationcomponent to separate these recyclable materials from the waste. Priorto separation of the combustible waste material into its variouscomponents, an automated bag opener may be used to open bags of wastematerial transported to a waste management plant from an externallocation such as a municipal refuse tip.

Preferably, the airless drier dries the combustible waste material withsuper-heated steam (typically at 135 to 145° C.) as the drying medium.In the airless drier, preferably drying is conducted in the absence ofoxygen to prevent the combustion of the combustible waste material.Accordingly, preferably the airless drier substantially prevents theingress of atmospheric air during a drying operation. To keep heat lossto a minimum, preferably the airless drier comprises an insulating outersurface to retain heat and to improve the overall energy efficiency ofthe system. Airless drying systems known in the art are described in GB2 281 383 A and GB 2 378 498 A.

In the systems and methods of the invention, the combustible wastematerial typically has an initial moisture (eg, H₂O) content in therange of 30 to 40% by weight. After drying of the combustible wastematerial in the airless drier, preferably the pyrolysis feedstock has amoisture content of 0 to 20% by weight, more preferably 2 to 18% byweight, and even more preferably 5 to 15% by weight.

Preferably, the waste management system further comprises a pyrolyserfor the pyrolysis feedstock to pyrolyse the dried combustible wastematerial and form char and pyrogas. Preferably, the pyrolysis of thefeedstock takes place at a temperature in the range of 250 to 600° C.Char is the solid residue product of the incomplete combustion oforganic materials. Pyrogas is typically defined as a combination ofgases including methane, water vapour, carbon monoxide and hydrogen inaddition to non-combusted volatile organic compounds present in thewaste materials, including tars and other high molecular weightcomponents.

Preferably, the waste management system further comprises a gasifier forconverting the char and/or pyrogas into syngas by a gasificationprocess. Syngas (otherwise known as “synthesis gas”) is defined as apure or near pure mixture of carbon monoxide and hydrogen generated fromthe high-temperature reaction of carbon present in char or other organiccompounds with water steam and air or oxygen. Preferably, gasificationtakes place at a temperature in the range of 850 to 900° C.

In one aspect of the invention, the airless drier comprises thepyrolyser. That is, the airless drier can be adapted with highertemperature (eg, 250 to 600° C.) settings than for its drying mode (eg,110 to 150° C.) to act as a pyrolysis apparatus. This has the benefit ofhaving one less component present in the system according to theinvention, thus providing waste management plant space and cost savings.

Preferably, the integrated waste management system includes an airlessdrier which generates heated steam output derived from the moistureextracted from the combustible waste material during the drying process,wherein a portion of the heated steam output which is otherwise releasedinto the atmosphere may be supplied to the gasifier to assist with theenergy and reaction requirements of the gasifier by providing heat andwater steam. This feature can contribute to the overall energyefficiency of the system according to the invention.

Preferably, the power generated according to the power generation systemand method of the invention is electrical power. Preferably, electricalpower production comprises the use of a steam cycle apparatus. The steamcycle apparatus may be a conventional steam turbine unit well-known tothe person skilled in the art. A portion of the heated steam output ofthe airless drier can be used to pre-heat the steam cycle of a steamturbine unit. Furthermore, the steam cycle apparatus may be adapted todirect heat energy to assist the energy requirements of the airlessdrier. This may be achieved by a direct transfer of heat energy or via aheat retention unit. Again, each of these features may assist incontributing to the overall energy efficiency of the systems accordingto the invention.

The steam turbine unit will typically comprise a boiler designed torapidly quench the exhaust gases which are generated in the oxidiser.Typically, this quenching of exhaust gas temperature is from 450° C. to200° C. Quenching over this temperature range preferably takes place inless than about 0.5 seconds. Rapid quenching of the exhaust gases is tominimise the potential for the de novo synthesis of toxic compounds suchas dioxins and furans in the boiler, which may be released into theatmosphere creating a pollution hazard. Such de novo synthesis is alsominimised because of the effectiveness of the sequential steps (eg,controlled temperature) of pyrolysis, gasification and oxidation stepsof the power generation system of the invention, which assists indestroying the precursors of de novo synthesis at each step.

Preferably, the power generation system of the invention furthercomprises a flue gas remediation unit for trapping pollutants releasedin either the pyrolysis, gasification or oxidation steps. This isbecause environmental pollution legislation is likely to require fluegas remediation of acid gases (eg, HCl, SO_(x) species, HF, etc), theremoval of particulates and the reduction of NO_(x) species from exhaustgases emanating from the oxidiser and/or steam turbine unit employed inthe present invention. This can be achieved by means of conventional wetor dry scrubbers. In particular, a sodium bicarbonate reagent inaddition to a bag filter may be used for the remediation of HCl, SO₂ andparticulate matter from exhaust gases. The use of a selective catalyticreduction unit can be used for the remediation of NO_(x). A temperatureof about 180 to 220° C., and preferably about 200° C., is typically theoptimal temperature for both of the remediation processes.

If flue gases are exhausted from the steam turbine unit at greater than200° C., energy is wasted. Accordingly, a heat recovery unit may beincorporated in the systems according to the invention typicallydownstream of a steam turbine unit. In practice, the heat recovery unitcools down the exhaust gases to about 140° C., thereby providing theoption of directing heat energy to the airless drier for the heating ofthe superheated steam heating medium. This improves the overallefficiency of a plant operating the system according to the invention.Typically, 140° C. is selected as a suitable exhaust flue gas exittemperature. This helps to prevent unsightly pluming at a stack outlet,acid gas condensation and as well provides heat to the airless drierwith a high temperature differential.

Alternatively, power may be generated according to the invention usingapparatus utilising the organic rankine cycle, the stirling cycle, thebrayton cycle, the direct combustion of syngas in a gas engine or a gasturbine, or in a fuel cell. Also, the provision of heat in the form ofsteam or hot water may be generated for process use or for refrigerationusing absorption chillers.

In an aspect of the invention, the oxidiser preferably comprises anoutlet and means for supplying surplus heat to the airless drier and/orthe pyrolyser. This can contribute to the overall energy and operationalefficiency of the system and enables the system to operate when localdomestic power demand may be reduced (eg, at night time), but theon-going production of the pyrolysis feedstock, pyrogas, char and syngasis desired.

The source of the combustible waste material may be any domestic orindustrial waste containing combustible materials. Such materials may befood scraps, paper, cardboard, plastics, rubber, clothing fabrics,garden waste and building materials such as wood. The combustible wastematerial is preferably an organic material.

The preparation of the combustible waste material for drying in theairless drier comprises the use of a separator. The separator mayinclude one or more components adapted for separating waste materialswith different physical properties. In particular, the separator mayinclude a trommel (a rotatable cylinder comprising holes for separatingmaterials by a pre-determined size) in series or alone for sorting thewaste material by size, a ballistic separator for sorting the wastematerial by weight, magnets for extracting and eliminating ferrousmetallic waste, an eddy current separator for extracting and eliminatingnon-ferrous metallic waste and an automated optical separator forextracting recyclable materials, such as plastics and glass. Valuablemetallic wastes and recyclable plastics materials may be shippedelsewhere for recycling. Furthermore, waste material considered toolarge or too heavy for the airless drying process may be transferred toa shredder for size and weight reduction as appropriate prior to drying.

As an example of a separation step for the combustible waste materialused in the system and methods according to the invention, a shipment ofwaste from a domestic refuse tip may be deposited in a trommel havingholes of a pre-determined size (eg, 80 mm in diameter) in its wall.Rotation of the trammel about its longitudinal axis results inseparation of the combustible waste material into a fine waste component(eg, <80 mm) and a bulky waste component (eg, >80 mm) dependent on thediameter of the trommel wall holes. The fine waste component issubjected to a magnetic separator for the extraction of non-combustibleferrous metals. It is then transferred to a vessel ready for feeding tothe airless drier. The bulky waste component is processed so thatmetals, plastics, glass and other recyclable and/or non-combustiblecomponents are removed. The processed bulky component is then subjectedto an automated optical separator to remove the remaining recyclablecomponents and is then fed to a shredder for conversion to a material ofsimilar particle size to the fine waste component. The shredded bulkywaste component is then transferred to the vessel containing the finewaste component ready for drying in the airless drier.

The airless dryer used in the present invention may employ drysuperheated steam as the heating medium for drying the combustible wastematerial. The use of super-heated steam in the airless drier has manybenefits over a conventional air drier as follows.

Because the specific heat capacity of steam is more than twice that ofair, more than twice the amount of heat can be transferred to theproduct being dried for the same mass flow of steam compared to heatedair. As a result, with the same temperature differential between themoist combustible organic waste material and the drying medium, the fanpower required to achieve a given heat transfer may be more than halved.

Further benefits of using super-heated steam are that due to its lowerviscosity than air (about 50% lower), it is able to percolate throughthe combustible organic waste material being dried, thereby speeding upthe drying process.

The airless dryer is typically a closed system which operates on fullrecirculation principles and not a combination of re-circulated watervapour/steam combined with ambient fresh air introduced during dryingfrom outside the dryer. Furthermore, indirect fired heat exchangers maybe used to prevent the ingress into the airless drier of ambient freshair which may lead to undesirable combustion of the material beingdried. Further, to prevent the ingress of ambient air (or significantquantities thereof) and steam leakage, the airless drier should beconstructed with a high level of air tightness. The absence ofoxygen-containing air in the drier during the drying process helpsprevents the combustion or explosion of flammable products present inthe combustible organic waste material during drying. The airless driermay be insulated to help prevent heat loss.

The pyrolyser indirectly heats the combustible waste material to a hightemperature (typically at about 600° C., but generally in the range of250 to 600° C.) in the absence of air or oxygen. This may be achieved bypassing the dried combustible waste material (pyrolysis feedstock)through a heated pyrolysis tube by means of an auger. The pyrolysis tubeis contained within a pyrolysis chamber through which hot exhaust gasesfrom the outlet of the oxidiser or another source may be passed. The hotexhaust gases pass over an outer surface of the pyrolysis tube andtransfer heat to the tube by convection and radiation. The hot pyrolysistube then transfers heat into the combustible waste material byconduction and radiation from an inner surface of the inner tube wall ofthe tube. The heat energy heats the combustible waste material typicallyto about 600° C. and thermally degrades the material to pyrogas andchar. The absence of air or oxygen prevents the combustible wastematerial from combusting within the pyrolysis tube. The benefits ofemploying the pyrolyser in the present invention include the productionof an excellent pyrolysis feedstock for the gasifier which is dry, hot,pre-pyrolysed and homogenous. This makes the subsequent operation of thegasifier simpler and more efficient.

Preferably, the pyrolysis chamber comprises an insulating outer surfaceto retain heat and to improve the overall energy efficiency of thesystems and methods according to the invention.

In another aspect of the invention, the pyrolyser may have a modulardesign with a single pyrolysis tube or a plurality of pyrolysis tubescontained within a pyrolysis chamber and/or one pyrolysis chamber or aplurality of pyrolysis chambers. These arrangements can help to optimisethe surface area in the pyrolyser to assist in the heat transfer fromthe heated gases from the outlet of the oxidiser or other source to thecombustible waste material being pyrolysed, thereby improving the energyefficiency of the system.

The gasifier receives the char and pyrogas from the pyrolysis tube ortubes. The char typically exits the pyrolyser from an outlet in apyrolysis tube and is transferred into the gasifier forming a char bedat a bottom inner surface of the gasifier. The gasifier is preferably anupdraft gasifier type, wherein steam and air are injected at a lowersurface of the char bed adjacent a bottom inner surface of the gasifierand percolates upwards through the char undergoing various chemicalreactions and reducing the steam and char to syngas comprising mostlycarbon monoxide and hydrogen. This reaction typically occurs at about850° C. and is self-regulating by means of the endothermic andexothermic nature of competing reactions and their different reactionrates at different temperatures. The syngas combines with pyrogas fromthe pyrolyser in the headspace above the gasifier char bed and all gasesare passed to the oxidiser by a pipe system. Residual ash containing asmall amount of unreacted carbon is discharged from an outlet in thebottom inner surface of the gasifier into an airtight ash container toprevent uncontrolled ingress of air into the bottom of the gasifier. Theresidual ash is disposed of.

The advantage of using an updraft gasifier is that it enables a simplegasifier design and is less sensitive to particle size, homogeneity andmoisture content than other types of gasifiers such as downdraftgasifiers or fluidised bed gasifier. The simple design of the updraftgasifier makes the gasifier easier to operate, more reliable and cheaperto build which are all advantages over other types of gasifier. However,a downdraft gasifier or a fluidised bed gasifier could if necessary alsobe used in accordance with the invention.

An updraft gasifier may further include a cyclone inducer for theheadspace gases. This facilitates a very low particulate loading in thesyngas or pyrogas which is transferred to the oxidiser for oxidising.The transfer of low levels of particulate material from the char presentin the gasifier to the oxidiser further assists in minimisingundesirable oxidation by-products from the exhaust gases of theoxidiser.

In one aspect of the invention, the gasifier may receive steam fordriving the gasification process from the outlet of the airless drier inorder to improve the overall energy efficiency of the systems andmethods according to the invention.

Preferably the gasification chamber comprises an insulating outersurface to retain heat and to improve the overall energy efficiency ofthe systems and methods according to the invention.

In another aspect of the invention, the arrangement of the pyrolyser andgasifier may be modular such that one pyrolysis tube or a plurality ofpyrolysis tubes may feed a gasifier and/or one gasifier chamber or aplurality of gasifier chambers may provide syngas to the oxidiser.

Syngas and pyrogas from the gasifier are supplied to the oxidiser bypipe. The oxidiser mixes the syngas and pyrogas with air where it isoxidised at high temperature to release chemical energy in the form ofheat. The oxidiser outlet temperature is controlled by adjusting theamount of excess combustion air that is introduced into the oxidiser.Good combustion is achieved by ensuring that the syngas (orsyngas/pyrogas mixture) and combustion air are mixed well in a turbulent(eg, cyclonic) environment with a long residence time at a hightemperature. Typically, during the oxidation process, the oxidisertemperature is maintained at about 1250° C., but it can be operated attemperatures as low as 850°C. Typically, the residence time of thesyngas (or syngas/pyrogas mixture) within the oxidiser is greater than 2seconds. Typically, good mixing and turbulence are achieved by injectingthe combustion air into the oxidiser at high velocity (greater than 20m/s) and directing the jet of combustion air (or plurality of combustionair jets) into the centre of a syngas (or syngas/pyrogas mixture)injection port. The air and syngas (or syngas/pyrogas mixture) isinjected tangentially to induce cyclonic rotation of the exhaust gaseswithin the oxidiser. This further mixes the combusted exhaust gases andmay also assist in trapping particulate materials present in the exhaustgases leading to a cleaner overall process.

Preferably, the oxidiser comprises an insulating outer surface to retainheat and to improve the overall energy efficiency of the systems andmethods according to the invention.

Preferably, the system according to the invention (eg, in the form of awaste management or power generation plant) is maintained under negativepressure. This may be achieved with the use of one or more induced draft(ID) fans. The use of the ID fans helps to ensure process safety where aleak or other failure in the system does not result in gases exiting thesystem, but atmospheric air enters instead. Care is generally taken toback-up an ID fan function so that a plant employing the system of theinvention is not left operating (and producing gas) without somenegative pressure being maintained.

Specific embodiments of the present invention are further described withreference to the drawings, in which:

FIG. 1 is a schematic diagram of an embodiment of a power generationsystem according to the invention comprising a waste management systemaccording to the invention.

FIG. 2 a is a schematic diagram of an embodiment of a waste managementsystem according to the invention showing the preparation of an airlessdrier (wet) feedstock.

FIG. 2 b is a schematic diagram of a power generation system accordingto the invention comprising a waste management system according to theinvention following on from the embodiment of FIG. 2 a with treatment ofthe airless drier (wet) feedstock through to power generation.

Referring to FIG. 1, there is an electrical power generation system 1having a combustible waste material source 2, a waste separator 3 forthe combustible waste material and an airless drier 4 for drying thecombustible waste material (not shown) to yield a pyrolysis feedstock(not shown).

System 1 has a pyrolyser 5 for producing char and pyrogas (not shown)from the pyrolysis feedstock, a gasifier 6 for producing syngas (notshown) from the char, and an oxidiser 7 for the high temperature (eg,˜1250° C.) oxidation of the syngas and pyrogas in the presence of air toproduce heat as depicted by arrow 8. The heat is used to generateelectrical power from a conventional steam turbine unit 9.

In use, combustible waste material from source 2 is supplied along belt10 to separation means 3 for separation into a combustible wastecomponent and other waste materials of value including recyclablematerials not for combustion, such as metal, glass, plastics, etc (notshown). The combustible waste component is then fed along belt 11 toairless drier 4 where it is dried at 110 to 150° C. using super-heatedsteam, until substantially all of the moisture (ie, primarily water) isremoved from the combustible waste to yield the pyrolysis feedstock.

The pyrolysis feedstock is transferred to pyrolyser 5 along enclosedbelt 12 for pyrolysis in an oxygen-free atmosphere at about 600° C.Pyrolysis results in a mixture of char and pyrogas (not shown). The charand pyrogas are transferred to gasifier 6 along pipe 13. The char isgasified in gasifier 6 at about 850° C. resulting in hydrogen and carbonmonoxide gaseous products (not shown) otherwise referred to as syngas.In an alternative embodiment, the airless drier 4 can also act as thepyrolysis apparatus when its operating temperature is increased to 600°C.

The syngas and pyrogas may alternatively be stored for later use or elseare transferred to oxidiser 7 along pipe 14 where combustion of thesyngas and pyrogas takes place at about 1250° C. generating heatdepicted by arrow 8 for driving steam turbine unit 9. Steam turbine unit9 generates electrical power which is fed into electrical grid 15, whichmay be a localised grid (eg, in a factory or processing plant) or elsepart of a domestic power supply grid.

Dependent upon the current energy requirements, at various stages ofsystem 1 excess heat energy 16,26 released by airless drier 4 or excessheat energy 17 released by oxidiser 7 can be selectively directed toassist the energy requirements of other components of system 1.Specifically, heat energy 16 in the form of steam evaporate can bedirected to gasifier 6. Heat energy 26 in the form of steam evaporatecan be directed to steam turbine unit 9 to preheat condensate returnwithin the steam turbine unit. Heat energy 17 from oxidiser 7 can bedirected to pyrolyser 5. Furthermore, excess heat energy 18 in the formof steam evaporate from turbine unit 9 can be directed to airless drier4. Excess heat as depicted by arrow 23 can be be transferred to heatrecovery unit 24 for transfer to airless drier 4 as depicted by arrow25. These options for heat energy feedback enables a series of efficientheat energy feedback mechanisms contributing to the overall energyefficiency and adaptability of system 1.

To further enable the energy efficiency of system 1, the variouscomponents may be partially or fully covered with heat-resistantinsulating layer 19,20,21,22 for improving heat retention in system 1.

Referring to FIG. 2 a there is a schematic overview of an aspect of anfurther embodiment of the waste management system according to theinvention, wherein a wet feedstock is generated for the airless drier(refer FIG. 2 b). FIG. 2 a shows the sequence of providing a combustiblewaste material and separation of the material into recyclable(combustible) components resulting in the drier (wet) feed stock as wellas non-combustible components (eg, metals) or combustible wastecomponents not desirable for combustion (eg, plastics).

Referring to FIG. 2 b there is a schematic overview of the continuationof the waste management process according to an embodiment of thepresent invention wherein the drier (wet) feed stock prepared accordingto the embodiment shown in FIG. 2 a is dried in an airless drier toyield a dried feedstock. The dried feedstock is pyrolysed to form charand pyrogas, the char and pyrogas is gasified to form pyrogas and syngasas well as an ash residue waste, and then the pyrogas/syngas mixture ismixed in a cyclone device prior to oxidisation with air to yield a hightemperature exhaust for heating a boiler to drive a conventional turbinefor power generation.

1. An integrated waste management system, comprising: a source of acombustible waste material; a separator for separating the combustiblewaste material from a recyclable material; an airless drier for dryingthe combustible waste material to generate a pyrolysis feedstock; apyrolyser for pyrolysing the pyrolysis feedstock to form char andpyrolysis gas; a gasifier for converting the char into syngas; and anoutlet in said airless drier for supplying heated steam output from theairless drier generated during pyrolysis feedstock generation to thegasifier.
 2. The integrated waste management system according to claim1, wherein the separator comprises one or more of a trommel, a magneticseparator, a ballistic separator, an eddy current separator, automatedoptical separation means and a shredder.
 3. The integrated wastemanagement system according to claim 2, wherein the airless drier isadapted is for drying the combustible waste material with super-heatedsteam as the drying medium.
 4. The integrated waste management systemaccording to claim 3, wherein the airless drier is sealed to prevent theingress of atmospheric air.
 5. The integrated waste management systemaccording to claim 4, wherein the airless drier comprises an insulatingouter surface.
 6. A power generation system comprising the wastemanagement system according to claim 5, further comprising an oxidizerfor the high-temperature oxidation of syngas and/or pyrolysis gasgenerated from the pyrolysis feedstock to generate heat for electricalpower production.
 7. The power generation system according to claim 6,wherein the power is electrical power.
 8. The power generation systemaccording to claim 7, wherein the oxidizer comprises an outlet forsupplying surplus heat to: (i) the airless drier; and/or (ii) thepyrolyser.
 9. The power generations system according to claim 8, whereinthe airless drier comprises an outlet for supplying steam evolved in thedrying step of the airless drier to the gasifier.
 10. The powergeneration system according to claim 9, wherein the system comprises asteam cycle apparatus.
 11. The power generation system according toclaim 10, wherein the steam cycle apparatus comprises a steam turbineunit for electrical power production.
 12. The power generation systemaccording to claim 11, further comprising a heat recovery unit forsupplying excess heat energy to the airless drier.
 13. The powergeneration system according to claim 11, further comprising a heatrecovery unit for supplying excess heat energy to the airless drier froma steam cycle apparatus.
 14. The power generation system according toclaim 13, further comprising a flue gas remediation unit for trappingpollutants.
 15. An integrated method of waste management comprising: (a)providing a source of a combustible waste material; (b) separating thecombustible waste material from a recyclable material present in thesource; (c) drying the combustible waste material in an airless drier togenerate a dried pyrolysis feedstock; (d) pyrolysing the dried pyrolysisfeedstock to form char and pyrolysis gas; (e) converting the char intosyngas in a gasifier; and (f) supplying heated steam output from theairless drier generated during pyrolysis feedstock generation to thegasifier.
 16. The integrated method of waste management according toclaim 15, wherein the source of combustible waste material is domesticwaste comprising food scraps, paper, cardboard, plastics, rubber, gardenwaste, clothing fabric and/or wood.
 17. The integrated method of wastemanagement according to claim 16, wherein separation of the combustiblewaste material comprises the use of one or more of a trommel, a magneticseparator, a ballistic separator, an eddy current separator, opticalseparation means and a shredder.
 18. The integrated method of wastemanagement according to claim 17, wherein the combustible waste materialis dried in the airless drier with the use of super-heated steam. 19.The integrated method of waste management according to claim 18, whereinthe combustible waste material is dried to yield a pyrolysis feedstockwith a moisture content of 0 to 20% by weight.
 20. The integrated methodof waste management according to claim 19, wherein the combustible wastematerial is dried to yield a pyrolysis feedstock with a moisture contentof 2 to 18% by weight.
 21. The integrated method of waste managementaccording to claim 20, wherein the combustible waste material is driedto yield a pyrolysis feedstock with a moisture content of 5 to 15% byweight.
 22. The integrated method of waste management according to claim15, further comprising power generation.
 23. The integrated method ofwaste management according to claim 22, wherein the power is electricalpower.
 24. The integrated method of waste management according to claim23, further comprising the steps of: (g) oxidizing the syngas andpyrolysis gas at high-temperature in an oxidizer to generate heat forpower generation.
 25. The integrated method of waste managementaccording to claim 24, wherein electrical power generation comprises theuse of a steam cycle.